Refrigeration apparatuses for cooling frozen food items etc. in transporting the items by land or sea have been known. Such a refrigeration apparatus includes a compressor and an evaporator, and air cooled in the evaporator is fed to a container as taught by, for example, Patent Document 1. The compressor of the refrigeration apparatus is driven by power generated by a diesel generator. The diesel generator is driven by a generator engine to generate power. Refrigeration capacity of the refrigeration apparatus is controlled by adjusting the degree of opening of a proportional inlet valve provided in a pipe on an inlet side of the compressor.